Problem: Christopher is 5 times as old as Omar and is also 8 years older than Omar. How old is Omar?
Answer: We can use the given information to write down two equations that describe the ages of Christopher and Omar. Let Christopher's current age be $c$ and Omar's current age be $o$ $c = 5o$ $c = o + 8$ Now we have two independent equations, and we can solve for our two unknowns. Since we are looking for $o$ , and both of our equations have $c$ alone on one side, this is a convenient time to use elimination. Subtracting the second equation from the first equation, we get: $0 =$ $5o$ $-$ $ (o + 8)$ which combines the information about $o$ from both of our original equations. Solving for $o$ , we get: $4 o = 8$ $o = 2$.